Another option would be to use the low-level build steps (which automate things like downloading and unzipping files) from BinDeps without actually using the full dependency handling tools (which, as @tkelman says, are only designed for libraries).
I ran into the same problem when trying to require the cmake executable, and I ended up creating a simple package https://github.com/rdeits/CMakeWrapper.jl that handles the cmake download and compilation on all platforms using the low-level BinDeps tools: https://github.com/rdeits/CMakeWrapper.jl/blob/master/deps/build.jl#L64